Rolling mill stand having axially adjustable intermediate rolls

ABSTRACT

A rolling mill has a pair of work rolls (12, 13), between which the work (14) is rolled and which are supported by respective back-up rolls (16, 15). Between one work roll (12) and its back-up roll (16) there are a pair of intermediate rolls (17, 18) which are axially adjustable relative to the other rolls.

This invention relates to a rolling mill stand having six or more rolls,including a pair of work rolls, each supported by at least one back-uproll, and intermediate rolls arranged between the work rolls and back-uprolls.

Such a mill is described in British patent specification No. 642767. InFIG. 7 of that specification there is illustrated an arrangement inwhich the intermediate rolls, arranged one between each work roll andits back-up roll, are axially adjustable to adapt the mill to a range ofstrip widths, the intermediate rolls being adjusted axially to make oneend of one roll aligned with one strip edge and the opposite end of theother roll aligned with the other strip edge. The specification furtherdiscloses tapers on the intermediate roll ends aligned with the stripedges.

A similar mill is described and illustrated in British patentspecification No. 1351074 where a 6-high configuration is adopted. Thatspecification further describes the use of conventional work rollbending for control of strip shape. In each of the arrangementsdescribed in the above specifications, aligning the ends of theintermediate rolls with the strip edges is claimed to reduceover-rolling of the strip edges when the barrel lengths of the workrolls exceeds the strip width. The axial adjustment of the intermediaterolls has a further benefit that work roll bending is no longer impededby the adjacent rolls at the strip edges.

The 6-high mill of specification No. 1351074, with an intermediate rollbetween each work roll and its back-up roll, does have a number ofpractical problems. Firstly, the mill is subject to asymmetrical loadingin the axial direction, the contact pressure between each work roll andits intermediate roll being non-uniform along the line of contactbetween the rolls. Asymmetrical loading can result in non-uniformheating of the work rolls along their barrels and consequently in shapecontrol problems, and in unequal surface wear problems. Secondly,removal of the lower intermediate roll at roll change is not easy andnecessitates special equipment in the mill window. Thirdly, the chocksfor the upper intermediate roll differ from those of the lowerintermediate roll--a complication which adds to the expense of the millwhen it is remembered that up to 100 sets of chocks may be needed forthe rolls.

In the present invention, at least two intermediate rolls are againprovided but those intermediate rolls are arranged between one of thework rolls and its back-up roll.

Normally the intermediate rolls are arranged in sequence, i.e. anintermediate roll engages the back-up roll and the other intermediateroll, while the other intermediate roll engages the first intermediateroll and the work roll. Alternatively, however, the two intermediaterolls may be arranged side-by-side, with each engaging both the back-uproll and the work roll.

It is convenient, particularly where the intermediate rolls are arrangedin sequence, to have those intermediate rolls between the upper back-uproll and the upper work roll in the case of a vertical mill, but ifdesired they may be arranged between the lower work roll and back-uproll.

Normally, only two intermediate rolls are provided, those rolls beingadjusted to bring an end of each intermediate roll to a position alignedwith a strip edge. However, there may be three intermediate rolls, withthe same ends of the uppermost and lowermost intermediate rolls alignedwith one strip edge and the opposite end of the middle intermediate rollaligned with the other strip edge; such an arrangement improves thesymmetry of loading of the mill stand.

The invention will be more readily understood by way of example from thefollowing description of a rolling mill stand in accordance therewithreference being made to the accompanying drawings, of which

FIG. 1 is a schematic representation of the rolls of the mill stand, and

FIG. 2 is a section view through a housing window.

In FIG. 1, the work rolls of the mill are indicated at 12 ad 13 with thestrip 14 to be rolled between them; as shown, the width of strip 14 issubstantially less than the barrel length of the rolls 12, 13. The lowerwork roll 13 is contacted and supported directly by a lower back-up roll15, while the upper work roll 12 is supported by its back-up roll 16through a pair of intermediate rolls 17 and 18; intermediate roll 17engages back-up roll 16, while intermediate roll 18 is betweenintermediate roll 17 and upper work roll 12. Each of the intermediaterolls is axially adjustable in the manner of the intermediate rolls ofthe above mentioned patent specifications and in use roll 17 is adjustedto bring its right-hand end into approximate alignment with theright-hand end of strip 14, while roll 18 is brought to a position withits left-hand end aligned with the left-hand end of the strip, again asshown. Preferably the aligned ends of rolls 17 and 18 are extended bytapers (not shown) as described in the earlier specifications and forthe purpose there explained. Work roll bending equipment is provided onrolls 12, 13 for shape control, the effectiveness of the equipment beingenhanced by the relatively small resistance to bending of roll 12 beyondthe edges of the strip. By virtue of the axial positioning of rolls 17and 18, over-rolling of the strip edge is diminished relative to thatoccurring in a conventional four-high mill, if not eliminated.

FIG. 2 shows the lay-out of one of the housing windows, the other beingsimilar. Starting at the bottom, a hydraulic capsule 20 acts on a chock21 at one end of lower back-up roll 15; chock 21 has wheels 22 which runon tracks 23 to enable the back-up rolls to be run out of the stand forroll change, when capsule 20 is collapsed.

The roll ends of work rolls 12 and 13 are carried in work roll chocks 24and 25, the lower chock 25 having roll change wheels 26 adapted to runon tracks 27. Chocks 24 and 25 have roll bending and balance cylinders28. Spring pots 39 are located in chock 25 to react against chock 24.The construction of the work rolls 12, 13 and the lower back-up roll 15,their chocks and roll balance and bending equipment, and their rollchanging equipment are similar to those of a conventional four-highmill.

The two intermediate rolls 17 and 18 have chocks 30 and 31 respectivelyand are located between blocks 32 and 33 attached to the housings andextending into the housing windows; they provide support for theintermediate rolls during axial adjustment relative to the other rolls(see FIG. 1). The blocks 32 and 33 carry roll change balance cylinders34 arranged, when operated, to act on wings 35 on chocks 30, 31. Theblocks 32, 33 also have axially arranged cylinders 36 for adjusting eachintermediate roll relative to the housings.

Finally, upper back-up roll 16 has its roll ends carried in chocks 37engaged by screws 38 in the tops of the housings.

Roll change is facilitated by having the intermediate rolls together.Thus, for work roll change, after having backed off the top back-uproll, the intermediate rolls are lifted by the cylinders 34 to clear thework rolls to enable the latter to be removed as a pair and replaced ason a conventional four-high mill. In the example shown in FIG. 2, thebottom back-up roll would be lowered away from the work rolls untilwheels 26 engaged track 27 and would then be further lowered to create agap between this roll and the lower work roll. At the same time, the gapcreated above the top work roll by the withdrawal of the upper rollassemblies allows the spring pots 39 to lift the top work roll chock 24clear of its balance cylinders 28. The assembly of the two work rollsmay then be withdrawn from the mill on the rails 27.

To change the intermediate rolls 17 and 18, the same procedure iscarried out but the top back up roll is further removed to enableclearances to be created between this roll and the upper intermediateroll 17 and, by the action of cylinders 34, between the two intermediaterolls. By inserting packers, or some other suitable devices, between thetop work roll chocks 24 and the lower intermediate roll chocks 31, andbetween the lower intermediate chocks 31 and the top intermediate chocks30, a stack of four rolls is created which then may bewithdrawn/replaced on track 27.

The intermediate rolls 17 and 18 are shown in FIGS. 1 and 2 as beinglocated between the upper back-up roll 16 and the upper work roll 12.That arrangement has the advantage that from the upper work roll 12downwards the stand layout can be identical with that of a conventionalfour-high mill, so that known and well-tried roll change equipment maybe utilised and no problem arises regarding floor level and access pits.Conversion of the mill to a four-high arrangement is also facilitated.However, the intermediate rolls may alternatively be positioned betweenthe lower work and back-up rolls 13 and 15, although the housingconstruction and the roll change equipment become more complicated.Also, while the use of only two intermediate rolls is preferred, morethan two such rolls may be employed if desired. For example, there maybe a third intermediate roll located between intermediate roll 18 andupper work roll 12 in FIG. 1, the upper intermediate roll 17 and thethird intermediate roll being adjusted together to bring theirright-hand ends into alignment with the right-hand edge of the strip 14.

In a further modification, the two intermediate rolls, instead of beingarranged in sequence as illustrated in the drawings, are arrangedside-by-side so that each engages both the back-up roll 16 and the workroll 12. As before, the intermediate rolls are axially movable, and areadjusted as before to bring the opposite ends of intermediate rollsapproximately to the vertical planes through the edges of the strip 14.

A rolling mill stand as described and illustrated or as modified asexplained above may be employed on its own as a single stand or may beone of a train of mill stands in a tandem mill. In the latter case, anyor all of the other stands of the train may have the describedconstruction or may be of a different construction, e.g. having aconventional four-high configuration.

We claim:
 1. A rolling mill stand having a roll stack comprising:(a)first and second work rolls; (b) first and second back-up rolls forsupporting said first and second work rolls respectively; (c) first andsecond intermediate rolls being located between and in contact with oneof said back-up rolls and said work roll supported by said one back-uproll, said first intermediate roll engaging said one back-up roll andsaid second intermediate roll, and said second intermediate rollengaging said first intermediate roll and said work roll; and (d) saidintermediate rolls being independently axially adjustable relative tothe other said rolls of said stack such that one end of eachintermediate roll can be aligned approximately with an edge of a stripbeing worked.
 2. A rolling mill stand according to claim 1, in whichsaid intermediate rolls are similarly constructed and have chocks whichare similarly constructed.
 3. A rolling mill stand according to claim 1,in which said intermediate rolls are arranged between the upper workroll and the upper back-up roll and are arranged to be withdrawntogether with said work rolls at roll change.